class Stack {
	constructor() {
		this.items = []
		// this.size = this.items.length
	}
	push(val) {
		this.items.push(val)
	}
	pop() {
		return this.items.pop()
	}
	peek() {
		return this.items[this.items.length]
	}
	isEmpty() {
		return this.items.length === 0
	}
	size() {
		return this.items.length
	}
	toString() {
		return this.items.join('').replace(/,/g, ' ')
	}
}
